Technical Field
The present application is directed generally to microphone arrays, and more specifically to better estimating a steering vector in microphone arrays utilizing minimum variance distortionless response (MVDR) beamforming where mismatches exist among the microphones forming the array.
Description of the Related Art
In today's global business environment, situations often arise where projects are assigned to team members located in different time zones and even different countries throughout the world. These team members may be employees of a company, outside consultants, other companies, or any combination of these. As a result, a need arises for a convenient and efficient way for these distributed team members to work together on the assigned project. To accommodate these distributed team situations and other situations where geographically separated parties need to communicate, multimedia rooms have been developed to accommodate multiple term members in one room to communicate with multiple team members in one or more geographically separated additional rooms. These rooms contain multimedia devices that enable multiple team members in each room to view, hear and talk to team members in the other rooms.
These multimedia devices typically include multiple microphones and cameras. The cameras may, for example, capture video and provide a 360 degree panoramic view of the meeting room while microphone arrays capture and sound from members in the room. Sound captured by these microphone arrays is critical to enable good communication among team members. The microphones forming the array receive different sound signals due to the different relative positions of the microphones forming the array and the different team members in the room. The diversity of the sound signals received by the array of microphones is typically compensated for at least in part by adjusting a gain of each microphone relative to the other microphones. The gain of a particular microphone is a function of the location of a desired sound source and ambient interference or noise. This ambient noise may simply be unwanted sound signals from a different direction that are also present in the room containing the microphone array, and which are also received by the microphones. This gain adjustment of the microphones in the array is typically referred to as “beamforming” and effectively performs spatial filtering of the received sound signals or “sound field” to amplify desired sound sources and to attenuate unwanted sound sources. Beamforming effectively “points” the microphone array in the direction of a desired sound source, with the direction of the array being defined by a steering vector of the array. The steering vector characterizes operation of the array, and accurate calculation or estimation of the steering vector is desirable for proper control and operation of the array. There is a need for improved techniques of estimating the steering vector in beamforming systems such as microphone arrays.